Acrylic-grafted nanocellulose hybrid double-network hydrogel with super-high toughness for water shutoff treatments

Hydrogels with high strength are strongly needed to perform such operations as fluid plugging and water shutoff in the oil & gas industry. In this work, a new type of tough hydrogel consisting of the acrylic acid grafted nanocellulose network and the copolymer (AA-co-AM) network was synthesized via one-pot free-radical polymerization, and further cross-linked by using Al3+. The prepared dual-crosslinked double network hydrogel (DN-Poly-X-CNF-g-AA) showed the high compressive strength and toughness at low concentrations of nanocellulose (within 0.2 wt%), i.e., the maximum compressive strength was 2.5 MPa at strains of 90% and the recovery rates exceeded to 90% after 10 compressive cycles. Meanwhile, the grafted nanocellulose endowed the double-network hydrogels with the strong intermolecular forces and the well-ordered hierarchical structure, which exhibited a high thermal decomposition temperature, solid-like elastic behavior and a swelling suppression. Finally, the sand-pack plugging experiments showed that the double-network hydrogels could effectively plug the porous media with different permeability, in which the breakthrough pressure gradient was between 4.9 and 104.63 MPa/m. The results demonstrated that the obtained tough hydrogel has a great potential to be applied as soft materials for water shutoff and conformance control in reservoirs.